Proportional fluidic amplifier

ABSTRACT

A proportional amplifier having tapering channel means to prevent overdrive and subsequent fluid loss thereby providing a fluidic element whose output pressure curve demonstrates a hard saturation characteristic.

United States Patent [72] Inventor Charles J. Ahern 3,233,622 2/1966Boothe 137/815 Sidney,N.Y. 3,326,463 6/1967 Reader 137/81.5X [21 Appl.No. 794,064 3,452,767 7/1969 Posingies. 137/815 [22] Filed Jan. 27, 19693,456,665 7/1969 Pavlin 137/815 [45] Patented Apr 20, 1971 Prima V ryExammerSamue1 Scott [73] Asslgnee The Bendix Corpomuon Attorneys RobertA. Benziger and Plante, Arens, Hartz,

Hix and Smith [54] PROPORTIONAL FLUIDIC AMPLIFIER 1 Claim, 4 DrawingFigs.

[52] US. Cl. 137/815 [51] Int. Cl. FlSc 1/04 [50] Field 01 Searchl37/8l.5

ABSTRACT: A proportional amplifier having tapering [56] References C'tedchannel means to prevent overdrive and subsequent fluid loss UNITEDSTATES PATENTS thereby providing a fluidic element whose output pressure3,181,546 5/ 1965 Boothe 137/815 curve demonstrates a hard saturationcharacteristic.

PATENTEU Arm I97! 22 sa my f he l4 PRIOR ART FIGUREI A CONTROL PREssuR EPR4 OR ART FiGURE 2 A OUTPUT PRESSURE A CONTROL PRESSURE FIGURE 4 CHARLES v d. AH ERN INVENTOR.

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ill PROPORTIONAL lFlLlUlllDllC AMPLIFIER SUMMARY OF THE INVENTION Thepresent invention relates to pure fluid amplifiers in general and tothose pure fluid amplifiers known as stream interaction proportionalamplifiers in particular. The stream interaction proportional amplifiersare well-known in the art and are characterized by their ability tocontrol high-energy fluid flows with relatively lower energy fluid flowsso as to controllably produce a high-gain pressure output or outputpressure ratio. These devices depend upon the direct relation shipbetween input and output for their functional utility. To achieve thisdirect relationship, steps are taken during the manufacturing process toreduce or completely eliminate the possiblity of the wall attachmenteffect occuring to disrupt the control/output relationship. These stepsusually involve removal of the sidewalls of the fluid interactionchamber in the vicinity of the power fluid stream and the addition ofvents to this area to prevent wall attachment in those zones where it isnot possible to remove the walls of the fluid interaction chamber. Thisresults in the unfortunate fact that excessive control pressures areable to partially or completely divert the power stream into thesevents. This, of course, results in loss of amplification and of outputpower as well as loss of power stream fluid. It is, therefore, an objectof the present invention to provide a proportional fluidic amplifierhaving means to prevent the operational losses which result fromexcessive control pressure dift erentials ln order to provide simple,reliable means to prevent the losses associated with overdrive offluidic proportional amplifiers, it is a further object of thisinvention to provide such means as do not rely upon feedback of aportion of the output flow to counter possible fluid control overdrive.The advantages of avoiding the feedback means controlling overdrive liein simplified fabrication and the avoidance of output pressure losseswhich result from feedback of a portion of output fluid signal.

BRIEF DESCRIPTION OF THE DRAWING FIG. ll shows the prior artproportional fluidic amplifier.

FIG. 2 shows the response curve for the prior art amplifier.

FIG. 3 shows a fluidic proportional amplifier made according to thepresent invention.

FIG. 4 shows the response curve for the proportional amplifier madeaccording to the present invention.

DETAILED DESCRIPTION OF THE DRAWING Referring now to FIG. I, a prior artproportional amplifier 110 is shown. The amplifier, as shown, is formedby forming the various passages in a piece of plastic 12 and placing thechannel-containing member 112 between two pieces of clear plastic M and16. Of course, many other methods of fabrication are known employing thesame or similar materials as well as employing dissimilar materials andthe invention herein described and hereinafter claimed is of advantagein all fluidic proportional amplifiers of whatever manner and materialof construction. In operation, a source of pressurized fluid, not shown,is communicated by known means to the fluid supply port 16. As the fluidis pressurized, a stream will be issued through nozzle 20 so as to crossthe interaction region 22 and impinge upon the splitter means 24. Thesplitter means M divides the fluid stream into two approximately equalstreams which then exit via outlet passages 26 and 28.

Control passage means 30 and 32 are shown as being at right angles tothe stream issued by nozzle 22, but this is merely illustrative andother configurations are possible. The control passage means 30 and 32are connected to means, not shown, for generating a control fluidsignal. These means may be, for instance, additional fluidic elements orany other source of control fluid. When the pressures are the same ineach of control passage means 30 and 32, the power fluid stream will beunefl'ected and the splitter means 24 will divide the fluid stream. Theratio of the division will then depend on whether the splitter issymmetrical or asymetrical. In the event that a slight imbalance existsin the relative pressures in control passage means 30 and 32, the powerfluid stream will be deflected toward the control passage having thelower relative pressure. This will result in the splitter means 24dividing the power fluid stream into two unequal streams which will exitvia the outlet passage means 26 and 28. The stream receiving the highestproportion of the fluid from the fluid source will, of course, be on thesame side of fluidic element as the control passage having the lowerrelative pressure. As is obvious, the proportion of the fluids receivedby the outlet passage means 26 and 28 depends on the relative pressuresin the control passage means 30 and 32 so that as the differentialpressure rises, the amount of power stream deflection increases andproportion of fluid received by the outlet passage on the low-pressurecontrol passage side approaches the totality of the fluid pressurestream.

Vent means 34 and 36 are operative to prevent wall attachment fromoccurring which would, of course, result in the power stream remainingin a deflected condition in the absence of control passage pressureimbalance of magnitude sufficient to overcome wall attachment effect.

FIG. 2 shows, by way of example, a graph of the output passage pressuredifferential plotted for various control passage pressure differentials.The control passage pressure differential is calculated by subtractingthe pressure in the right control passage 30 from the pressure in theleft control passage 32. The output passage pressure differential iscalculated in the reverse manner, that is, pressure in the left outputpassage 26 is subtracted from the pressure in the right output passage28. This reversal represents the actual reversal experienced by thefluidic element since higher pressure in the left control passage 32produces high output pressure in right output passage 28. As can beobserved, the output pressure differential increases rapidly forrelatively slight changes in the control passage pressure differential.This, of course, is characteristic of this class of elements. Maximumpoints 50 and 52 represent those points at which all fluid issued by thepower nozzle 20 is being directed to either the left or the right outputpassage.

However, due to the necessity of maintaining laminar flow andundisturbed ingress of the fluid to the output passages 30 and 32, theprior art teaches that the output passages must maintain a substantiallystraight passage wall on the portion of the output passages opposite thesplitters or flow-dividing means in the vicinity of fluid impact. Thisresults in a situation which prevents the proportional fluidic amplifierfrom operating effectively in a condition of hard saturation. Thestraight passage wall terminates in a sharp edge as the outlet passageenters the region of the vent. This sharp edge unintentional serves as asplitter whenever a hard saturation condition exists and causes powerstream fluid to enter the vents rather than the intended outlet passage.This is represented by the not quite so steep slope which occurs almostimmediately after the output pressure differential has achieved itsmaxima 50 and 52.

Referring now to FIG. 3, a proportional fluidic amplifier is shownsubstantially similar to that shown in FIG. 1. For the sake of clarity,numeral identification remains the same where possible. It will beobserved that the present invention differs from the prior art only inthe inlet region of the output passages. Instead of terminating in asharp edge, the wall portion of the output passages 26 and 28 oppositethe splitter means 24 flaits outwardly from the splitter means 24forming intercept wall means 60 and 62 each of which forms an obliqueangle with the centerline of the output passage. With reference to FIG.4, I have found that the response curve for the amplifier, according tomy invention, contains substantial zones of sustained high-pressureoutput and 152 over a considerable region of increased control pressuredifferential where the prior art device almost immediately began to loseoutput pressure if the control passage pressure differential increasedbeyond the optimum value. This can be explained by the fact that as thepower fluid stream attempts to deflect beyond the centerline of theoutlet passage, the stream begins to impinge upon the intercept wallwhich tends to redirect the stream back toward the centerline of theoutlet passage. This then gives the proportional amplifier, according tomy invention, a hard saturation characteristic which permitssatisfactory operation over a wider range of pressure differentials andalso permits sustained satisfactory operation at or near its maximumoutput pressure differential without resort to control means external tothe element.

lclaim: l. A proportional fluidic amplifier comprising: a fluidinteraction region; means for issuing a power fluid stream into saidinteraction region; output passage means in communication with saidinteraction region for receiving said power fluid stream; controlpassage means communicating with said interaction region forcontrollably establishing and applying a pressure difierential to saidpower fluid stream;

splitter means in cooperation with said output passage means tosegregate power fluid stream flow through said output passage means;

control fluid means in fluid-conducting relation with said controlpassage means to provide the pressure differential for controlling powerfluid stream flow through said output passage means; and

intercept means comprising the inlet of said output passage meansoperative to permit hard saturation of the amplifier;

said intercept means comprising straight wall portions of said outputpassage means;

said output passage means wall portions flairing outwardly away fromsaid splitter means;

said wall portions operative when said power fluid stream of a portionthereof impinges thereupon to redirect said power fluid stream orportions thereof toward the centerline of said output passage means.

1. A proportional fluidic amplifier comprising: a fluid interactionregion; means for issuing a power fluid stream into said interactionregion; output passage means in communication with said interactionregion for receiving said power fluid stream; control passage meanscommunicating with said interaction region for controllably establishingand applying a pressure differential to said power fluid stream;splitter means in cooperation with said output passage means tosegregate power fluid stream flow through said output passage means;control fluid means in fluid-conducting relation with said controlpassage means to provide the pressure differential for controlling powerfluid stream flow through said output passage means; and intercept meanscomprising the inlet of said output passage means operative to permithard saturation of the amplifier; said intercept means comprisingstraight wall portions of said output passage means; said output passagemeans wall portions flairing outwardly away from said splitter means;said wall portions operative when said power fluid stream of a portionthereof impinges thereupon to redirect said power fluid stream orportions thereof toward the centerline of said output passage means.